Voice operated intercommunication system



Jan. 7, 1958 s. s. BRODY 1 VOICE OPERATED INTERCOMMUNICATIDN SYSTEMFiled Nbv. 17, 1953 STANLEY. 5. 535m ATTORNEYS VOICE OPERATEDINTERCONIMUNICATION SYSTEM Stanley S. Brody, Brooklyn, N. Y.

Application November 17, 1953, Serial No. 392,776

Claims. (01. 119 1 ,1

--(GrantetLunder Title 35, U. Code (1.952), sec. 266) operationalrestrictions upon the manufacturers and users of. theequipment. One ofthemajor. defects of an intercommunication system'is-. the .well knowneffect of feed back with "the resultant "high :pitchi noise. 'Allconventional intercommunication systems contain a microphone,an-"amplifier and 4a speaker;r:. 'Il1e audible energy that impingesuponthe microphone, is converted into electrical energyA The'electricalenergy atz'the output of the micro phone" is theninserted': into anamplifier'to increase the level of the electrical energy to a new valuewithout any alteration'in thetype or the graphic form of the energywave.- l-lhe outputof the amplifier is then-fed to a speaker where theelectrical energy is converted back into the original form of audibleenergyat an increase in energy level. If the output of the speaker wereto be inserted into the microphone, the new output would be at a greaterenergy level. The cycle 'of increasing the energy input and greaterspeaker output would continue until the amplifier reached saturation.The end result of the above type of feedback and saturation is a loudhigh pitch tone that emits from the speaker.

Feedback will occur whenever the speaker and the microphone of a systemare in close proximity to each other. The energy wave from the speakercan cause feedback by entering the microphone directly or indirectly.Numerous methods-have been devised to counteract the objectional effectof feedback. They usually encompass complicated, expensive and sensitiveequipment and circuit arrangements that result in high initial costs,high failure rate and-increased maintenance costs. Many of the devisedmethods decrease, rather than eliminate, the possibility of feedback.

One of the common methods that is utilized to eliminate the possibilityof feedback is the use of a talk-listen key thatis operated by the userto conform withthe act being performed. The operation of a talk-listenkey is objectional in that the user must develop a certain amount ofcoordination to carry on a conversation. This type of intercommunicationsystem requires the use of v the operators hand thus preventing him fromdoing all but the most elementary duties while talking into the intertothe input of an amplifier and, through a relay, to the output oftheother amplifier. A difierential relay that is connected to the outputof each amplifier through a rectifier, determines the transducer thatshall perform as a speaker and the transducer that shall perform as amicrophone. At any particular instant during the operation, oneamplifier will be operating into a transducer that functions as aspeaker while the output of the other amplifier will be grounded toprevent feedback and will be disconnected from all transducers.

To operate, the user talks into one of the transducers. A differentialrelay that is triggered by the output of the activated amplifier,automatically connects the second transducer to the output of theactivated amplifier, grounds the output of the other amplifier andremoves the transducer from the output of the grounded amplifier. Thedifferential relay is of the quick-make, slow-break type so that theoperating amplifier will remain opera tive during the short pauses thatare common to normal speech.

It is a general object of the present invention to provide anintercommunication systemthatis completely free of the effectoffeedback. T

It is another object to present an intercommunication system wherein theswitching is performed automatically.

An additional object is to provide an intercommunication system thatwill allowa two-way conversation without requiring the user tomanuallyoperate any control device. w Other objects and many of theattendant advantages of this invention willbe readily appreciatedasthesame becomes better understood by reference to the following :detaileddescription when considered .in'connection with the accompanyingdrawings wherein; v Fig. 1 is a block and schematic diagram of theinvention wherein the switching is performed .by three relays, one ofwhich is a diiferential relay and Fig. 2 is a block and schematicdiagram of a modified form of the invention wherein the switching isperformed by two relays. Y

Referring to Fig. 1, permament magnet speakers or transducers 2 and 4are of conventional-design and construction well known in the art. Theamplifiers 6 and-8 are also of conventional design.

' Each speaker or transducer 2 and 4 is capable of operation either as atransmitter or as a receiver. Such speakers are old in the art. Thevoice coil of each speaker is connected to the input of a correspondingamplifier 6 or 8, respectively. The outputs of amplifiers 6 and 8 areeach connected to a corresponding speaker through the normally opencontacts of the relays 10 and 12, respectively. The relays 10 and 12connect the appropriate transducer to the output of the proper amplifierat the required instant. The output of the amplifier 6 is also connectedto operate one side 13 of a differential relay 14, through a rectifier16. The dif-. ferential relay is of the normally open type. The outputof the amplifier 6 is also connected directly to ground 3 through thenormally open contacts 20 of side 15 of the differential relay 14. Theoutput of the amplifier 8 is connected to operate the other side 15 ofthe relay 14 through a similar rectifier unit. The output of theamplifier 8 .is also connected directly to ground 3 through the normallyopen contacts 18 of theside 13 of the relay 14. The circuits of thecoilsof the relays 10 and 12 are completed when connected to groundthrough another pair of normally'open contacts 22 and Mrespectively ofthe relay 14.

Each transducer is connected To operate this invention, the amplifiers 6and 8 .are turned on. -The transducers 2 and.4 are conveniently locatedat the desired locations that are usually known as stations. When theapparatus onstation. is in the.

facts of relays 10, '12 and 14' are "open? "At'the instant somebodyspeaks into the transducer or transmitter and receiver}, theintelligence is .con v e rted into electrical energy fand amplifiedbytheamplifier output of the amplifier 6 actuates the side our the relay 14through the action of the rectifieri16. The closing of the contacts 18and 22 of the" relay 1,4 grounds the output of the amplifier Sandactuates' the relay 10. f The closing of the contacts of the relayconnects the output of the amplifier 6 to the other transducer 4. "Atthis instant, the direction of intelligence is from transducer 2 totransducer 4 through amplifier 6. 'At this point the output of theamplifier 8 is grounded, thus preventing feedback and making thetransducer 4 completely serviant to the transducer, 2. The transducer '2is not connected to the output of the amplifier 8 because -relay 12 isopen at this time, but performs as a'mici'ophone for the amplifier 6.The relay 14 is of the q uicki'make, slow'break type so that thetransducer Twill retain control during the short pauses that occurduring'nor'mal conversion. The transducer 4 can never gain controlwhile'the transducer 2 has controL- The "contacts 18 a'r'1d22 of the relay 14andthe contacts o'f' the relay 10 o'penwhen the flow of intelligenceinto the speaker 2' stops for a time interval that is equal to orgreater than the drop-out time of the relay 14. When this conditionoccurs, the transducer 2 can regain control, or the transducer 4 cantake control and make the speaker 2 the serviant transducer. The relay12 and-sideof m'ereiay' '14 o per'ate in the same sequence and' ma'nneras thei'elay 10'andside 13 operate.

The form of invention shown in Fig. 1 may be constructed in a'modifiedform, "such as shown in Fig. 2. For example,-'the relay' 14' mayhe'inthe form of two separate relays 113' and} 115 an the"quick-make-slowbreak type instead of one differential t ype of relay.The relays 10 and 12 maybe eliminatedby adding another set of normallyopen contacts llqa'nd 112 to the relays 113 and 115. 1lfiis 'alsoobvioiis thaf'one'of the amplifiers 6 or 8 may b e in-sea from thecircuit by the utilization of thefproper s'v'vitcfin {not shown).

Obviouslymany modificatioiis and "variations of the present inventionare possible in the light of the above teachings. 'i lt therefore'to' beunderstood that 'within the scope ot the appended claims'ithe inventionmay be practiced otherwise' thanspecifically described.

What is claimed is: p

l. A voice operatedintercommunication'system"comprising aplurality oftransducers 'of the' transmitting and receiving type, a plurality-"ofamplifiers connected to said transducers, means connected to the outputsides of said'amplifiers to ground the outputs of all but one of theamplifiers to prevent signal generation'feedback and means to connectthe transducers 'ofthegrounded amplifiers to the output of theungrounded amplifier, said grounding means and saidtransducer-connection means being actuated by the output of theungrounded amplifier to form a communication circuit comprising thetransducer which receives the voice energy, the ungrounded amplifier and'thetransducers which are connected to the output of the ungroundedamplifier.

2. A voice operated intercommunication system having a sending and areceiving station comprising a first and a second transducer of thetransmitting and receiving type, a first amplifier coupled to receive asignal from mid transducers, a second amplifier coupled to receive asignal from said transducers, a ground, and means tothe output of'saidfirst amplifier when said first transducer is receiving voice energy. 1

3. A voice operated intercommunication system having a sending and areceiving station comprising a first transducer of the transmitting andreceiving type to generate a signal, a second transducer of thetransmitting and receiving type, a first amplifier coupled to receivethe signal from said first transducer, a second amplifier coupled toreceive a signal from said second transducer, a ground, and a relaycoupling the output from said first amplifier to said second transducerand the output of said second amplifier to said ground when said firsttransducer is receiving voice energy, and coupling the output from saidsecond amplifier to said first trans ducer and the output of said firstamplifier to ground when said second transducer is receiving voiceenergy, so that speaking into either of said transducers automaticallyforms a communication circuit comprising the energy-receiving transduceroperating as a microphone, its associated amplifier and the othertransducer operating as a speaker.

4. A voice operated intercommunication system having a sending and areceiving station comprising a first transducer of the transmitting andreceiving type, a first amplifier coupled to said transducer to generatean amplified signal, a second transducer of the transmitting andreceiving type, a second amplifier coupled to said second transducer togenerate an amplified signal, first and second rectifiers coupled toreceive such amplified signals and to convert a portion of such signalsto direct current, a ground, and switching means coupled to said firstand second transducers and amplifiers, said first and second rectifiersand said ground, said switching means being selectively actuated by theoutput of either one of said amplifiers, Whose associated transducer isreceiving voice energy, to ground the output of the other amplifier andto form a communication circuit comprising the energyreceivingtransducer operating as a microphone, its associated amplifier and theother transducer operating as a speaker.

5. A voice operated intercommunication system having a sending and areceiving station comprising a first transducer of the transmitting andreceiving type, a first amplifier coupled to said transducer to generatean amplified signal, a second transducer of the transmitting andreceiving type, a second amplifier coupled to said second transducer togenerate an amplified signal, first and second rectifiers coupled toreceive such amplified signals and to convert a portion of such signalsto direct current, a ground, and a difierential relay coupled to saidfirst and second transducers and amplifiers, said first and secondrectifiers and said ground, said difierential relay being selectivelyactuated by the output of either one of said amplifiers, whoseassociated transducer is receiving voice energy, to ground the output ofthe other amplifier and to form a communication circuit comprising theenergy-receiving transducer operating as a microphone, its associatedamplifier and the other transducer operating as a speaker.

6. A voice operated intercommunication system having a sending and areceiving station comprising a first transducer ofthe transmitting andreceiving type, a first amplifier coupled to said transducer to generatean amplified signal, a second transducer of the transmitting andreceiving type, a second amplifier coupled to said second transducer togenerate an amplified signal, first and second rectifiers coupled toreceive such amplified signals and to convert a portion of such signalto direct current, a ground, a difierential relay coupled to said firstand second amplifiers and to said ground to selectively feed the outputsof said amplifiers to ground and means coupled to said differentialrelay to feed the outputs of said amplifiers to said transducers, saidlast-named means being actuated by operation of said difierential relaywhich, in turn, is actuated by the output-of either one of saidamplifiers whose associated transducer is receiving voice energy, sothat speaking into either of said transducers automatically forms acommunication circuit comprising the energy-receiving transduceroperating as a microphone, its associated amplifier, and the othertransducer operating as a speaker, while grounding the output of theother amplifier.

7. A voice operated intercommunication system having a sending and areceiving station comprising a first transducer of the transmitting andreceiving type to generate a signal, a first amplifier coupled to saidfirst transducer to receive the generated signal, a first rectifiercoupled to the output of said first amplifier to convert a portion ofthe output signal to direct current, a second transducer of thetransmitting and receiving type, a second amplifier coupled to saidsecond transducer, a second rectifier connected to the output of saidsecond amplifier to convert a portion of the output signal to directcurrent, a ground, a first relay having a coil connected to receive adirect current from said first rectifier and having two sets of normallyopen contacts, one set connected between the output of said firstamplifier and said second transducer and the other set connected betweenthe output of said second amplifier and ground, and a second relayhaving a coil connected to receive direct current from said secondrectifier and having two sets of normally open contacts, one setconnected between the output of said second amplifier and said firsttransducer and the other set connected between the output of said firstamplifier and ground, so that speaking into either of said transducersactuates the relay whose coil is connected to the rectifier whichreceives the output signal of the amplifier associated with theenergy-receiving transducer, whereby the output of the other amplifieris grounded and a communication circuit is formed comprising theenergy-receiving transducer operating as a microphone, its associatedamplifier and the other transducer operating as a speaker.

8. A voice operated intercommunication system having a sending and areceiving station comprising a first amplifier, a first transducer ofthe transmitting and receiving type coupled to said first amplifier togenerate and feed a signal to said first amplifier, a rectifier coupledto the output of said first amplifier to convert a portion of the outputsignal to direct current, a second amplifier, a second transducer of thetransmitting and receiving type coupled to said second amplifier togenerate and feed a signal to said first amplifier, a rectifier coupledto the output of said second amplifier to convert a portion of theoutput signal to direct current, a ground, a differential relay having apair of coils each connected to one said rectifier and to ground andhaving two sets of normally open contacts, a second relay having a coilconnected to one of the sets of contacts on said differential relay andhaving a set of normally open contacts connected between one of saidtransducers and the output of its non-associated amplifier, a thirdrelay having a coil connected to the other of the sets of contacts onsaid differential relay and having a set of normally open contactsconnected between the other of said transducers and the output of itsnon-associated amplifier, said differential relay being actuated by theoutput signal from one of said amplifiers whose associated transducer isreceiving voice energy, t e actuation of said differential relay in turnactuating said second and third relays, so that speaking into either ofsaid transducers automatically forms a communication circuit comprisingthe energyreceiving transducer operating as a microphone, its associated amplifier and the other transducer operating as a speaker, whilegrounding the output of the other amplifier.

9. A voice-operated intercommunication system comprising in combination:at least two transducers of the transmitting and receiving type; atleast two amplifiers, each connected to a diiferent one of saidtransducers; and switching means connected to said amplifiers and saidtransducers for selectively disabling one of said amplifiers when thetransducer associated with the other said amplifier is receiving voiceenergy and for connecting the non-utilized transducer at that time tothe output of the non-disabled amplifier, said switching means beingactuated by output signals from the amplifier whose associatedtransducer is receiving voice energy.

10. A voice-operated intercommunication system comprising, incombination: at least two transducers of the 'transmitting and receivingtype; at least two amplifiers,

each connected to a difierent one of said transducers; and switchingmeans connected to said amplifiers and said transducers for selectivelygrounding the output of one of said amplifiers when the transducerassociated with the other said amplifier is receiving voice energy andfor connecting the non-utilized transducer at that time to the output ofthe ungrounded amplifier, said switching means being actuated by outputsignals from the amplifier whose associated transducer is receivingvoice energy.

References Cited in the file of this patent UNITED STATES PATENTS2,102,903 Levique Dec. 21, 1937 2,424,069 Tschumi July 15, 19472,477,275 Tschumi July 26, 1949 2,545,489 Levy Mar. 20, 1951

